as above HoneyBadger is right with his suspicion.
you only need to enable nfs and share a folder. vsphere 5.5 can only use NFSv3 and can only use the user 'root' to connect (can't configure otherwise). So you need to configure no_root_squash, which essentially you do with the mapping.
in the setting of your nfs share "Maproot User" select "root" (default is N/A)